This invention relates to a process for producing xanthan gum from Xanthomonas campestris NRRL B-1459.
Polysaccharides or gums that function to control the flow properties of aqueous systems have a wide variety of uses including oil well drilling and fracturing, food additives, textile printing, paint additives and the like. Of the presently employed polysaccharides or gums, the most widely used is xanthan gum which is derived from a sugar or starch by fermentation with Xanthomonas campestris. Xanthan gum dissolves in water to produce a high viscosity solution at very low concentrations and has the property of controlling rheological properties of fluids. Xanthan gum solutions are highly pseudoplastic in that the viscosity decreases rapidly as the rate of shear on the solution is increased. This relationship is instantaneous and reversible. In contrast to most polysaccharides, the viscosity of xanthan gum solutions is essentially constant over the range of about 25.degree. F. to about 200.degree. F. In addition, xanthan gum has excellent thermal stability and maintains its viscosity even when salts such as sodium chloride are added thereto. Because of these properties, xanthan gum has been the thickener of choice particularly in oil well drilling fluids and in oil recovery processes as well as in a wide variety of other industrial applications.
Xanthan gum presently is produced by an aerobic submerged fermentation in a medium containing a carbon source such as 1-5% glucose. Upon completion of the fermentation, the fermentation liquor is pasteurized and the polysaccharide is recovered by precipitation such as with an alcohol, e.g. methanol, ethanol, isopropyl alcohol. The resultant gum product then is dried and milled and is useful for forming high viscosity solutions.
It would be highly desirable to provide a means for stimulating the production of xanthan by the fermentation of Xanthomonas campestris. Such a process would provide higher yields of the gum thereby obtaining substantial economic benefit and improved efficiencies in the production of xanthan gum.